import com.sun.deploy.panel.ITreeNode;

import java.util.Deque;
import java.util.LinkedList;

public class BinaryTree {

    static class TreeNode {
        public char val;
        public TreeNode left;//左孩子的引用
        public TreeNode right;//右孩子的引用

        public TreeNode(char val) {
            this.val = val;
        }
    }


    /**
     * 创建一棵二叉树 返回这棵树的根节点
     *
     * @return
     */
    public TreeNode createTree() {
        TreeNode A = new TreeNode('A');
        TreeNode B = new TreeNode('B');
        TreeNode C = new TreeNode('C');
        TreeNode D = new TreeNode('D');
        TreeNode E = new TreeNode('E');
        TreeNode F = new TreeNode('F');
        A.left = B;
        A.right = C;
        B.left = D;
        B.right = E;
        C.left = F;
        return A;
    }

    // 前序遍历
    public void preOrder(TreeNode root) {
        if (root == null) {
            return;
        }
        System.out.print(root.val + " ");
        preOrder(root.left);
        preOrder(root.right);
    }

    // 中序遍历
    void inOrder(TreeNode root) {
        if (root == null) {
            return;
        }
        inOrder(root.left);
        System.out.print(root.val + " ");
        inOrder(root.right);
    }

    // 后序遍历
    void postOrder(TreeNode root) {
        if (root == null) {
            return;
        }
        postOrder(root.left);
        postOrder(root.right);
        System.out.print(root.val + " ");
    }

    public static int nodeSize;

    /**
     * 获取树中节点的个数：遍历思路
     */
    void size(TreeNode root) {
        if (root == null) {
            return;
        } else {
            nodeSize++;
            size(root.left);
            size(root.right);
        }
    }

    /**
     * 获取节点的个数：子问题的思路
     *
     * @param root
     * @return
     */
    int size2(TreeNode root) {
        if (root == null) {
            return 0;
        }
        return size2(root.left) + size2(root.right) + 1;
    }


    /*
     获取叶子节点的个数：遍历思路
     */
    public static int leafSize = 0;

    void getLeafNodeCount(TreeNode root) {
        if (leafSize != 0) {
            leafSize = 0;
        }
        if (root == null) {
            return;
        }
        if (root.left == null && root.right == null) {
            leafSize++;
        }
        getLeafNodeCount1(root.left);
        getLeafNodeCount1(root.right);
    }

    void getLeafNodeCount1(TreeNode root) {
        if (root == null) {
            return;
        }
        if (root.left == null && root.right == null) {
            leafSize++;
        }
        getLeafNodeCount1(root.left);
        getLeafNodeCount1(root.right);
    }


    /*
     获取叶子节点的个数：子问题
     */
    int getLeafNodeCount2(TreeNode root) {
        if (root == null) {
            return 0;
        }
        if (root.left == null && root.right == null) {
            return 1;
        }
        return getLeafNodeCount2(root.left) + getLeafNodeCount2(root.right);

    }

    /*
    获取第K层节点的个数
     */
    int getKLevelNodeCount(TreeNode root, int k) {
        if (root == null || k < 1) {
            return 0;
        }
        if (k == 1) {
            return 1;
        }
        return getKLevelNodeCount(root.left, k - 1) + getKLevelNodeCount(root.right, k - 1);
    }

    /*
     获取二叉树的高度
     时间复杂度：O(N)
     */

    int getHeight(TreeNode root) {
        int l = 0;
        int r = 0;

        if (root == null) {
            return 0;
        }
        l = getHeight(root.left) ;
        r = getHeight(root.right);
        return l > r ? (l+1) : (r+1) ;
    }


    // 检测值为value的元素是否存在
    TreeNode find(TreeNode root, char val) {
        if (root == null) {
            return null;
        }
        if (root.val == val) {
            return root;
        }
        TreeNode result = null;
        find(root.left, val);
        if (result != null) {
            return result;
        }
        find(result, val);
        return null;
    }

    //层序遍历
    void levelOrder(TreeNode root) {
        Deque<TreeNode> deque = new LinkedList<>();
        if (root != null) {
            deque.add(root);
        }
        while (!deque.isEmpty()) {
            if (deque.peek().left != null) {
                deque.add(deque.peek().left);
            }
            if (deque.peek().right != null) {
                deque.add(deque.peek().right);
            }
            System.out.print(deque.pop().val + " ");
        }
    }


    // 判断一棵树是不是完全二叉树
    boolean isCompleteTree(TreeNode root) {
        Deque<TreeNode> deque = new LinkedList<>();
        if (root != null) {
            deque.add(root);
        } else {
            return false;
        }
        while (deque.peek() != null) {
            if (deque.peek().left != null) {
                deque.add(deque.peek().left);
            }
            if (deque.peek().right != null) {
                deque.add(deque.peek().right);
            }
            deque.pop();
        }
        while (!deque.isEmpty()) {
            if (deque.pop() != null) {
                return false;
            }
        }
        return true;
    }
}